GUTs & Planck Scale: Unifying Gravity?

In summary, the conversation discusses the SUSY GUT scale and its relation to the Planck scale, as well as the potential role of gravity in superstrong spontaneous symmetry breaking. Witten's work on string-based model building is mentioned as a potential advancement in this area. Additionally, a reference to Witten's Heinrich-Hertz Lecture is provided, which further explores these ideas. There are also mentions of papers discussing octonions and their applicability in these discussions.
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arivero

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In 1981 Dimopoulous, Raby and Wilczek, considering SUSY GUT, remark that In the ordinary theory [itex]M \approx 10^{15} GeV[/itex] and ... so the supersymmetric [itex]M \approx 10^{18} GeV[/itex]. This is the same ordeor of magnitude as the Planck mass, hinting perhaps a larger unification including gravity as well

Before in 1974 Georgi, Quinn and Weinberg already were suggesting this scent: It is intriguing that we are let to contemplate elementary particle masses as high as 2 10E17 GeV, or about the same order of magnitude as the Planck mass, G^1/2=1.2206E19 GeV. Perhaps gravitation has something do to with the superstrong spontaneus symmetry breaking, or perhaps the spontaneus breakdown of the simple simple gauge group has something to do with setting the scale of the gravitational interaction.

In fact the current estimates for the SUSY GUT scale are still, I believe, at about a close factor, 1/400, of the Planck scale. It seems that any theory of quantum gravity should reflect about it. Do they?
 
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  • #2
yes the "inline tex" format "itex" makes it smaller but better placed so I can see better in one case. before you changed it, there was some overwriting.

It seems that any theory of quantum gravity should reflect about it. Do they?

I don't know of any. Or right now I cannot bring any to mind that do. maybe someone else can. I will try to remember and perhaps can dredge something up.
 
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  • #3
(I corrected the typos, thanks Marcus)

marcus said:
I don't know of any. Or right now I cannot bring any to mind that do. maybe someone else can. I will try to remember and perhaps can dredge something up.

Of course Witten do, he somewhere presents string-based model building as an step forward in this scale-catching, even if smaller than the jump from GUT to SUSY GUT.
 
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arivero said:
Of course Witten do

I have just read a related, interesting, description from Witten in pages 607-608 of his Heinrich-Hertz Lecture
 
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marcus said:
thanks for the reference. I had never looked at this talk, given at DESY in 2002. In case anyone's interested, the abstract is here:
http://arxiv.org/abs/hep-ph/0207124

I find amusing that two of the 9 (*) papers quoting this talk are about octonions; when I was reading Witten's arguments about going up in the ladder of inclusion for GUT groups I was thinking on the resemblance with typical discussions in the newsgroups about moving forward to use quaternions and then octonions.


(*) Yep, 9 citations! Between the arxived Witten papers more than one year old, it is the 6th least cited paper and the 9th least read.
 
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1. What is the Planck scale and why is it important in unifying gravity?

The Planck scale is the scale at which quantum effects of gravity become significant, and it is the smallest scale at which meaningful measurements can be made. It is important in unifying gravity because it is the scale at which the laws of gravity and quantum mechanics must be reconciled.

2. Can general relativity and quantum mechanics be unified at the Planck scale?

At the Planck scale, the laws of general relativity and quantum mechanics break down and cannot be reconciled. This is known as the "Planck scale problem" and remains one of the biggest challenges in modern physics.

3. What is the role of Grand Unified Theories (GUTs) in unifying gravity?

GUTs are theories that attempt to unify the three fundamental forces of nature (electromagnetism, strong nuclear force, and weak nuclear force) at high energies, including the Planck scale. They provide a framework for understanding how gravity can be incorporated into the unified theory.

4. How does string theory attempt to unify gravity at the Planck scale?

String theory is a theoretical framework that attempts to unify all of the fundamental forces of nature, including gravity, by describing particles as tiny vibrating strings. It predicts that at the Planck scale, particles are not point-like but have a length scale, thereby reconciling the discrepancies between general relativity and quantum mechanics.

5. Are there any experimental evidence or observations that support the unification of gravity at the Planck scale?

Currently, there is no experimental evidence or observations that directly support the unification of gravity at the Planck scale. However, some theories, such as string theory, make predictions that may be tested in the future through high-energy experiments or observations of the early universe.

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